With the widespread use of high-quality smart phones, Pads and other portable electronic products, people have increasingly higher requirements for earphones that can be cooperatively used with them. These earphones are required to be small in size and, meanwhile, have high fidelity acoustical quality performance reproducing a variety of sound effects. In addition, for any kind of the above-mentioned electronic products, in order to allow users to listen to the sound signals provided by electronic products without disturbing others, the earphone has become a necessary accessory for each electronic product. In addition, the earphone also provides a better sound transmission for the listener, so that the listener can clearly hear and understand the content of the sound signals.
The existing earphones can be classified into in-ear earphones, on-ear earphones, and half in-ear earphones according to different wearing manners. The earphone mainly includes a front housing, a rear housing, and a speaker received inside of the front and rear housings of the earphone. Different users have different preferences for the frequency response of the earphone, and it is also necessary to adjust the frequency response of the earphone according to different using environments to meet the users' needs. Therefore, there is a need for an earphone that can adjust the frequency response of the earphone according to individual needs, so that a single type of earphone can exhibit different musical styles, so as to adapt to different users and using environments.